The invention concerns an exhaust gas aftertreatment apparatus for an internal combustion engine.
Stationary internal combustion engines are frequently used for decentral power generation. They have up to 24 cylinders. The cylinders are generally disposed in two cylinder banks in a V-arrangement. Stationary internal combustion engines are frequently equipped with exhaust gas aftertreatment systems in order to comply with emission requirements. For example, oxidation devices in the form of oxidation catalysts are used to reduce the emission of unburnt hydrocarbons and carbon monoxide. Catalysts for selective catalytic reduction are frequently used for the reduction of nitrogen oxides. Systems for exhaust gas aftertreatment of stationary internal combustion engines therefore frequently include catalytically active assemblies, referred to hereinafter as catalyst units.
In operation of such catalyst units, it can be indicated that only a part of the exhaust gas mass flow from the internal combustion engine flows through the catalyst unit while the remaining part is passed around the catalyst unit by way of a bypass conduit. Temperature peaks in the exhaust gas downstream of the catalyst unit can be alleviated by that exhaust gas bypass. That is relevant in particular when the catalyst unit is arranged upstream of an exhaust gas turbocharger. Excessive exothermic phenomena occur for example in regeneration of the catalyst unit or when unburnt hydrocarbons break through, for example in the event of misfires. Another motivation for passing exhaust gas around the catalyst unit by way of a bypass is the occurrence of untreated emissions from the internal combustion engine, that are harmful to the catalyst unit, for example by virtue of operating with high-sulfur fuel.
Thus, WO 2012/123636 shows an arrangement of a stationary internal combustion engine having a catalyst unit 3 (here in the form of an oxidation device) which is set up upstream of the exhaust gas turbine 2. In accordance with that specification, the exhaust gas can be passed around the catalyst unit 3 by way of a bypass conduit 6 when using high-sulfur fuel.
In the case of exhaust gas aftertreatment apparatuses which are known from the state of the art for stationary internal combustion engines, having a bypass conduit, the bypass conduit is in the form of a pipe separate from the catalyst unit. No consideration is given to a structural form of the internal combustion engine. That entails a number of disadvantages: on the one hand, the structural configuration is complicated and expensive while on the other hand the exhaust gas which is passed by way of a bypass conduit does not contribute to heating the catalyst unit.